1. Field of the Invention
The present invention generally relates to fasteners and tools for operating such fasteners and particularly to tamper-proof fastener and a driver tool with complementary driver head contact for operating the same.
2. Description of the Prior Art
Fasteners of various types have been developed in the art to meet various fastening requirements. Examples of conventional fasteners are screws, bolts and rivets. Depending on requirements and applications, screws and bolts with various head designs and patterns such as slotted, Phillips and hex have been developed. These conventional fasteners, however, are easily operated on and therefore tampered with as driver heads with corresponding head designs and patterns are readily available.
For special applications where the fasteners as applied need to be tamper-proof, fasteners with special head designs and driver tools with complementary head designs must be used.
The prior art discloses tamper-proof fastener and driver tool of various head designs and means.
U.S. Pat. No. 5,269,208 to Kolvites et al. discloses a tamper-proof fastener whose head has a generally frusto-conical shape defining a circular flat top and a circular base of larger diameter, three short noses separated 120 degrees apart projecting from the sloped side of the drive head. The head of the drive tool for this fastener has a complementary frusto-conical socket.
U.S. Pat. No. 4,938,108 to Mekler discloses a theft resistant fastener system wherein both rotatable wrench and head of fastener have at least three ball-and-socket joints distributed about the fastener axis.
U.S. Pat. No. 4,827,811 to Vickers discloses a tamper-resistant torque-responsive fastener having a socket which is of substantially triangular shape with rounded corners and curved sides disposed on the head. Also provided is a driving tool for operating the fastener.
U.S. Pat. No. 4,430,035 to Rodseth discloses a fastener driver head and tool and coupling therebetween wherein fastener driver head comprises a substantially circular disc-shaped base portion, a plurality of frustoconical portions integrally formed with the base portion and a plurality of ribs alternating with the frustoconical portions. The mating driver tool has a recessed driving head or socket substantially complementary with the fastener head.
U.S. Pat. No. 4,426,896 to Kesselman discloses a tool for removing an in situ tamper-proof fastener of the type disclosed in U.S. Pat. Nos. 4,037,515 and 4,225,165 and includes spikes located and oriented on a body to snag the head of the fastener so that rotation imparted to the body is transferred to the fastener.
U.S. Pat. No. 4,258,596 to Bisbing et al. discloses a tamper-resistant fastener wherein the fastener head has three sockets, at least one of which is eccentrically disposed with respect to the other two. The fastener may be attached and removed only with the application of a special tool having a male portion adapted for matable engagement with the fastener head.
U.S. Pat. No. 4,171,662 to Simone et al. discloses a security screw wherein its head has an odd number of sides arranged symmetrically with respect to the center of the head and inclined to the axis of the screw. The screw is removed by the use of a matching socket wrench.
U.S. Pat. No. 4,125,051 to Herkes et al. discloses a tamperproof fastener having a low profile head whose upper surface is configured to include a very short cylindrical boss, coaxial of the fastener and a plurality of ribs extending radially outwardly therefrom formed on an otherwise flat, circular flange. The ribs include a perpendicularly disposed driving surface of low height extending from the flat surface and an angled camming surface intersecting with the driving surface.
U.S. Pat. No. 4,018,111 to Goldhaber disclosed a tamper resistant fastener having a head portion of a circular contour, the upper surface of which is provided with a circular bore at a location which eccentrically disposed with respect to the longitudinal axis of the shank portion of the screw. The tool has a coupling key at its end which is received within the head bore of the screw such that rotation of the handle of the tool will cause rotation of the screw.
Although these prior arts disclose various tamper-resistant and tamper=proof methods and devices, none of them disclosed a tamper-proof fastener and driver tool for operating the same of the particular type as disclosed and claimed hereinafter.
It is thus a primary objective of the present invention to provide a tamper-proof fastener and driver tool for operating the same having a novel driving contact wherein a fastener so formed can only be operated by a complementary driver tool.
Another objective of the present invention is to provide a tamper-proof fastener and driver tool for operating the same wherein it is virtually impossible to operate on the fastener without the complementary driver tool.
Yet another objective of the present invention is to provide a tamper-proof fastener and driver tool for operating the same wherein the fastener can de removed non-destructively only with an authorized driver tool having complementary driving contact.